Ultrastructure of hepatitis B virus surface antigen(HBsAg)produced by transformed yeast was analyzed with high-resolution negative staining and ice embedding. By negative staining, HBsAgs produced by yeast were either spherical, or slightly elongated. Their mean diameter and length were27.5nm and32.5nm respectively. They were angular in outline, and consisted of many subunits whose diameter was about4.3nm. Each subunit had a hollow. Thus, it became apparent that yeast HBsAg was bigger(about27.5nm)than HBsAg derived from human plasma(about21nm). Also, yeast HBsAg showed hollow-subunit structure about4.3nm in diameter, whereas human HBsAg showed knob-like subunits about3nm in diameter. These morphological differences between yeast and human HBsAg may be attributable to that the yeast HBsAg is mainly composed of disulfide-bonded dimers of polypeptides lacking glycosylated side-chains, whereas the human HBsAg is composed of polypeptides with or without glycosylated side-chains.By ice embedding, where specimens are hydrated and unfixed, yeast HBsAgs were either spherical, or slightly elongated, and had electron-lucent centers. They were smooth in outline, and had jelly-like appearances. Their mean diameter and length were 23.7nm and27.0nm respectively. The apparent bigger size of negatively stained yeast HBsAg may have been caused by flattening due to surface tension when they were dried in air; the size measured by ice-embedding may give a true value.

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The vascular anatomy of subterranean rhizome and root of Ophioglossum vulgatum was studied. The vascular cylinder of the rhizome which had developed adventitiously is ectophloic siphonostele with endarch primary xylem maturation. In the basal part of the rhizome ectophloic siphonostele reveals a complete cylinder of vascular tissue, whereas an ectophloic siphonostele with overlapping gaps occurs in the upper part of the rhizome. Each meristele is arranged as collateral bundle. The bulk of primary xylary elements in the vascular bundles is radially aligned. The roots are monarch with exarch xylem maturation and the monarch vascular pattern reveals opposite arrangement of xylem and phloem. The relation between stelar and total root diameter shows a low correlation. No signs of secondary thickening are found either in the rhizomes or the monarch roots. The comparison of anatomical features of vascular system of the rhizome and root with other ferns shows significant differences.

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Morphological transition of cap differentiation at the stalk-apex of a giant unicellular alga, Acetabularia caliculus, was observed with a scanning electron microscope. Beginning with a ring-shaped arrangement of primary protuberances, cap-rays were differentiated after the successive development of primary, secondary and tertiary protuberances. The insides of these protuberances were separated into cavities by septa, however these cavities were continuous with each other due to perforation of the septa. Through the pores on the septa, protoplasmic streaming and central vacuole were continuous in all of the cavities and they were also continuous in a whole cell. Based on these structures, the homology and synchrony in the cap-morphogenesis were discussed, concerning turgor pressure.

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Process of architecture formation was quantitatively analyzed for Viburnum dilatatum and V. wrightii(Caprifoliaceae). In both species, orthotropic primary axes emerge from the basal parts of mother plants near the ground level. Terminal buds of vegetative shoots and paired axillary buds on the most distal nodes of reproductive shoots elongate dominantly in the following year. The architecture of the primary axes is formed by four branching patterns: a monopodial pattern(M), a sympodial pattern producing a pair of opposite daughter shoots(SP), a sympodial pattern producing a single daughter shoot(SS), and a pattern terminated with a dormant or dead bud(D). Process of the architecture formation is composed of four successive stages: 1)height growth, where the M pattern is dominant; 2)crown formation, the M pattern decreased gradually, while the SP and SS patterns occur; 3)crown expansion, the M and SP patterns are frequent; 4)over mature, the M pattern becomes dominant again. The primary axes grow vigorously only within a first few years of their development. Axillary buds of them emerge after several years' dormancy and form orthotropic secondary axes. For Viburnum dilatatum, nearly50%of the primary axes develop the secondary axes, and the secondary axes also elongate vigorously. Furthermore, more than20%of the secondary axes form the tertiary axes, and only10%of the tertiary axes form the quarternaryaxes. On the contrary, only less than25%of Viburnum wrightiis primary axes form the secondary axes which do not elongate vigorously. This speceis entirely does not form tertiary axis. Consequently, Viburnum wrightii forms more simple architecture than V. dilatatum.

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The entire process of the interspecific protoplast fusion between Candida tropicalis and Candida boidinii was observed by transmission electron microscopy(TEM). The protoplasts of the two heterologous strains were fused in medium containing filtersterilized polyethylene glycol, Ca&sup2+; and sorbitol for5to120min. Specimens were taken at appropriate time intervals and prepared for TEM. Protoplasts of the two strains were distinguished by their size as well as by the electron density of the mitochondrial matrix. Changes in the cell membrane of protoplasts were visible immediately after incubation in the fusion medium, and successive changes were noted in the ultrastructure: 1 cell membrane contact between the heterologous protoplasts; 2 waving of the membranes at the site of contact of the protoplasts; 3 flattening of the cell membrane; 4 rupturing and discontinuity of the cell membranes at the site of contact; 5 mixing of cytoplasms of the heterologous protoplasts near the ruptured cell membranes; 6 invisibility of the membranes at the fusion site; 7 nuclear fusion;and 8 completion of the protoplast fusion. These results show that karyogamy and plastogamy occur immediately after incubation of the protoplasts in a fusion medium.

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In order to see whether a confocallaser scanning microscope(CLSM)is a useful tool for studies on the microtubule(MT)organization in plant cells, the spatial distribution of MTs in root tip cells of Allium cepa L. was examined using a CLSM. As the resolution of the image is improved using a CLMS, we could clearly detect MTs connecting between the spindle and the preprophase band(PPB)at late prophase stage. Although it was not easy to analyze the developmental process of spindle MTs on the nuclear surface using a conventional fluorescent microscope because of the strong flourescent signal from the PPB, a stereo pair image reconstructed from a focal series of images enabled us to see the detailed process of MT organization on the nuclear surface. Based on these results, the utility and problems of CLSM are discussed.

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The meiospores are produced by reduction divisions and are a stage of the sexual reproduction. The reproduction correlated to the meiospore should be separated from the asexual reproduction in the typology of reproductions.

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